5 Ways Redshift Create Temp Table

Amazon Redshift is a fully managed data warehouse service that allows users to analyze data across multiple sources and perform complex queries. One of the key features of Redshift is its ability to create temporary tables, also known as temp tables, which can be used to store data temporarily during the execution of a query. In this article, we will explore 5 ways to create a temp table in Redshift, along with examples and best practices.

Method 1: Creating a Temp Table using the CREATE TEMP TABLE Statement

The CREATE TEMP TABLE statement is used to create a temporary table in Redshift. The basic syntax of this statement is as follows:

CREATE TEMP TABLE table_name (
  column1 data_type,
  column2 data_type,
 ...
);

For example, to create a temp table called "sales" with two columns, "id" and "amount", you can use the following statement:

CREATE TEMP TABLE sales (
  id INT,
  amount DECIMAL(10, 2)
);

Example Use Case: Creating a Temp Table for Data Transformation

Suppose you want to transform a dataset by converting all date columns to a standard format. You can create a temp table to store the transformed data and then use it for further analysis.

CREATE TEMP TABLE transformed_data (
  id INT,
  date DATE,
  amount DECIMAL(10, 2)
);

INSERT INTO transformed_data (id, date, amount)
SELECT id, TO_DATE(date, 'YYYY-MM-DD'), amount
FROM original_data;

Method 2: Creating a Temp Table using the CREATE TABLE Statement with the TEMP Keyword

Alternatively, you can create a temp table using the CREATE TABLE statement with the TEMP keyword. The syntax is similar to the CREATE TEMP TABLE statement:

CREATE TABLE table_name (
  column1 data_type,
  column2 data_type,
 ...
) WITH (TEMP);

For example, to create a temp table called "sales" with two columns, "id" and "amount", you can use the following statement:

CREATE TABLE sales (
  id INT,
  amount DECIMAL(10, 2)
) WITH (TEMP);

Example Use Case: Creating a Temp Table for Data Aggregation

Suppose you want to aggregate data by grouping it by a specific column. You can create a temp table to store the aggregated data and then use it for further analysis.

CREATE TABLE aggregated_data (
  category VARCHAR(50),
  total_amount DECIMAL(10, 2)
) WITH (TEMP);

INSERT INTO aggregated_data (category, total_amount)
SELECT category, SUM(amount)
FROM original_data
GROUP BY category;

Method 3: Creating a Temp Table using a Common Table Expression (CTE)

A common table expression (CTE) is a temporary result set that you can reference within a SELECT, INSERT, UPDATE, or DELETE statement. You can use a CTE as an alternative to a temp table in Redshift.

WITH temp_table AS (
  SELECT column1, column2,...
  FROM original_table
)
SELECT * FROM temp_table;

For example, to create a temp table called "sales" with two columns, "id" and "amount", you can use the following CTE:

WITH sales AS (
  SELECT id, amount
  FROM original_data
)
SELECT * FROM sales;

Example Use Case: Creating a Temp Table for Data Filtering

Suppose you want to filter data based on a specific condition. You can create a CTE to store the filtered data and then use it for further analysis.

WITH filtered_data AS (
  SELECT *
  FROM original_data
  WHERE amount > 100
)
SELECT * FROM filtered_data;

Method 4: Creating a Temp Table using a Subquery

A subquery is a query that is nested inside another query. You can use a subquery to create a temp table in Redshift.

SELECT * FROM (
  SELECT column1, column2,...
  FROM original_table
) AS temp_table;

For example, to create a temp table called "sales" with two columns, "id" and "amount", you can use the following subquery:

SELECT * FROM (
  SELECT id, amount
  FROM original_data
) AS sales;

Example Use Case: Creating a Temp Table for Data Sorting

Suppose you want to sort data based on a specific column. You can create a subquery to store the sorted data and then use it for further analysis.

SELECT * FROM (
  SELECT *
  FROM original_data
  ORDER BY amount DESC
) AS sorted_data;

Method 5: Creating a Temp Table using a View

A view is a virtual table that is based on the result of a query. You can create a view to store data temporarily and then use it for further analysis.

CREATE VIEW temp_table AS
SELECT column1, column2,...
FROM original_table;

For example, to create a view called "sales" with two columns, "id" and "amount", you can use the following statement:

CREATE VIEW sales AS
SELECT id, amount
FROM original_data;

Example Use Case: Creating a View for Data Analysis

Suppose you want to analyze data based on a specific condition. You can create a view to store the data and then use it for further analysis.

CREATE VIEW analyzed_data AS
SELECT *
FROM original_data
WHERE amount > 100;

SELECT * FROM analyzed_data;

In conclusion, Redshift provides several ways to create temporary tables, including using the CREATE TEMP TABLE statement, the CREATE TABLE statement with the TEMP keyword, common table expressions, subqueries, and views. By following best practices and using temp tables judiciously, you can improve the performance and efficiency of your Redshift queries.

Remember to use temp tables sparingly and only when necessary, as they can consume additional resources and impact query performance. Additionally, be sure to drop temp tables when they are no longer needed to avoid cluttering your database and to ensure that your queries continue to run efficiently.